A blog about science because it's a wonderful thing. No real theme, just topics I chose to write about because I understand them (biological science, mostly to do with viruses). I am a PhD student in Cell and Molecular biology, studying immune defence to viral entry, at University College London (credentials). Enjoy...

Tuesday, 30 August 2011

On The Origins Of HIV (part 3 of 3)

There may be some who have recently read my blog posts and have disagreed with some of the things I stated. HIV, like many other things, is surrounded with conspiracy theories, so I will now contemplate a few of these and hope to give evidence to suggest why they deserve to be called conspiracy.

The first of these theories is one that had the most support for a certain time, the idea that HIV was produced in a lab in America and not as a product of natural evolution of SIV, following its zoonosis. This theory was touted very strongly by some individuals. The idea that HIV was man-made goes hand in hand with a further conspiracy that it was made for biological warfare against black and homosexual people. A door-to-door survey, conducted in California by Klonoff and Landrine in 1999, found that 27% of the black Americans they spoke to believed that HIV had been made in a government lab. A further study, this time a telephone survey conducted by Bogart and Thorburn, found that 20% of men and 12% of women strongly agreed with the statement “AIDS is a form of genocide against blacks.” They also found that 30% of men and 27% of women agreed with the statement “HIV was produced in a government lab.”

It was claimed that HIV was produced under the auspices of the Special Virus (Cancer) Program, which ran in the US between 1962 and 1978, and tested on human subjects – starting the pandemic. At the time the claim was made, the dates of the evolution of SIV to HIV had not been fully elucidated and the earliest known examples of HIV were those first found in America in 1983. Since then it has been calculated that HIV is much older than that (between 1884 and 1924 as I explained in post 2) and that the first known sample of HIV was found in the Belgian Congo in 1959. I suppose we can’t rule out for certain that HIV wasn’t produced in a lab between 1962 and 1978 but this would not have been the start of the pandemic spread.

A second conspiracy to be considered centres around the production of the hepatitis B vaccine. This vaccine began pilot testing in the US in the early 70’s and was given to gay men to help stop the spread of the hepatitis B virus (HBV). In order to produce the vaccine it was necessary to grow it in chimpanzee cells. It is therefore argued that the vaccine may have become contaminated with SIV, which then entered humans through injection of the vaccine, allowing the mutation to HIV. For a time the dates seemed to fit, the vaccine began production in the early 70s and the first known case of HIV was 1983. However, as with the theory of its production in a lab, much earlier examples of HIV were later found which lay to rest the idea that the HBV vaccine was to blame for the existence of HIV.

The last theory to consider involves another vaccine, this time the oral polio vaccine (OPV). In 1955, Jonas Salk produced the inactivated polio vaccine (IPV), which quickly made a massive impact on the number of cases of polio worldwide. Later, in 1962, Albert Sabin produced OPV which, instead of a dead form of the polio virus, used a much weakened version (an attenuated form) which gave much more specific (and therefore better) immunity. In order to make the poliomyelitis virus attenuated so as not to cause symptoms it was necessary to grow it in chimpanzee cells. As had been argued with the HBV vaccine, Edward Hooper in his book The River, put forward the idea that chimp cells may have been infected with SIV, thus giving the chance for SIV to enter humans and mutate. This idea was strongly refuted and it was argued that the chimp cells could not have contained SIV because measures would have been taken to avoid such contamination. Further evidence against OPV as the cause of HIV can be found in the fact that, as the name implies, OPV is given orally and the stomach and intestines are highly adapted to prevent the entry of any infectious agent, making it highly unlikely that, had the vaccine been contaminated with SIV, it would have been able to enter the human blood stream. And finally, once again, the dates just don’t fit given the finding of a HIV positive patient from 1959.

So the origins of HIV were once shrouded in mystery and conspiracy with many people believing it to have been man-made and some going as far as believing it to be made for use as a biological weapon. However, as is often the case, the more science looked into the true origins of the virus the more the evidence piled up against these conspiracies. It is now generally accepted that HIV was formed through natural evolution following the transmission of SIV to a human host, most likely through the preparation of bush meat in West Africa sometime in the late 19th or early 20th century. There are those who still won’t fully accept these facts but I hope that I have managed at least to show that the science behind the origin of HIV is far more compelling than any covered up wrong-doing, deliberate creation or accidental contamination of a vaccine.

So that concludes the first of my science blog posts. I hope I have at least provided some information and education if no more than that. Stay tuned for more of my blog - I'm not sure what will be next; I’ll see what takes my fancy.